Molecular characterisation of poliovirus inactivation with formaldehyde or other alternative chemical compounds

As the Global Polio Eradication Initiative progresses towards its conclusion inactivated poliovirus vaccine (IPV) is increasingly being used on a routine basis to ensure that any re-introduced viruses do not spread. However the current administration of conventional IPV (cIPV) includes a risk of wild seed viruses escaping from manufacturing facilities. To address this risk IPVs could instead be prepared from Sabin live attenuated strains. However Sabin IPV (sIPV) type 2 has been found to induce a lower level of antibodies than type 2 cIPV. The reason (s) for this difference is not clear as little is known about the molecular mechanisms that underpin the formaldehyde inactivation process. To investigate the process of inactivation and its consequences, this study has analysed the effect of inactivation on different aspects of poliovirus biology. As serotype 2 shows the greatest differences between sIPV and cIPV, a range of type 2 poliovirus strains with varied antigenic and biological properties have been inactivated using formaldehyde and alternative chemicals. The effect of inactivation on the viral antigenicity and immunogenicity of the poliovirus strains has been assessed using methods for the pre-release control of vaccine batches and various novel techniques including a biosensor-based technique and immunisation-challenge experiments in transgenic mice. Both the virus strain and inactivation chemical affected the potency of inactivated preparations. The effect of inactivation on the functionality of the viral RNA and the ability of inactivated virus to bind and undergo the conformational changes necessary to enter the target cell have been investigated using real-time RT-PCR and FACS flow cytometry. Inactivation modified the viral RNA and prevented poliovirus virions from undergoing necessary conformational changes. This research will contribute to better understanding the differences between sIPV and cIPV and will help to develop new/modified inactivation protocols to produce IPVs with improved immunogenicity